Metal drawing



Patented Apr. 10, 1945 (UNITE STATES PATE T OFFICE METAL DRAWING ltaymond E. Slater, New Rochelle, N. Y.,.assignor #toRemington ArmsCompany, Inc., Bridgeport, "Conn, a corporation of Delaware 4Application May 20, 1944, .Serial No. 536,478

" 9. Claims. (01. 205-8)- The present invention relates to adrawing die,particularly for the drawing of tubular or shell shaped articles, suchfor instance as bullet jacket components produced by one or moredrawingoperations from a cup shaped blank or apreviously drawn shell.

In the drawing of a tubular article the tubular wall is usually drawn toa greater height at one side than the other, this unevenness in the tubesides being due in part to the fact that the wall of the cup from whichthe shell is drawn is usually slightly uneven in height, and thisunevenness increases with each successive drawing operation. The usualtype of drawing die is provided with a relatively short land, this beingnecessitated in practice in order to prevent excessive frictional dragsuch'as might occur in the case of a relatively high land. Where theheight of the land is less than the maximum disparity between the highand low sides of an unevenly drawn tube the long side of the tube whichis still to be drawn is worked to a greater thickness than the otherportions of the tube. This thicker portion or lip will be deformed bybending and this bending is usually great enough to induce furtherbending in subsequent drawing operations. Also, as the last portions ofthe metal on the short side of the tube are being pulled out of the 'diland the pressure difierential builds up from zero to its maximumamount, and this variation in pressure on the last few particles on theshort side works height between the long and short sides of ,the .drawnarticle, the short side will be supported by the die land while the longside is being sized between the punch and the 'die land. This isimpractical, however, because of the increased frictional drag due tothe increased land height and because the total compressive forcedeveloped increases with an increase in land height,

' with the result that the forces exerted on the die of the drawnarticle is supported by the die landwhile the end portion of the longside is being sized between the punch and a die land, to the end thatthe tube wall remains straight and is of uniform thickness throughout.It is particularly proposed to provide a multiple land die, whereinadjacent die lands are of identical diameter and are separated by aclearance groove,

the metal. so that the wall is bent inwardly toward the axis of the tubein a curvilinear manner, Consequently the metal which forms the inwardradius is decreased in thickness by the squeezing action oi the die andthe deflected punch. Thus, a drawn tube having uneven sides may beconsiderably bent at its end, the high side may be substantially thickerthan the normal wall thickness of the tube, and the short side may besubstantially thinner. The current practice, to obvi- 7 die land beforeany portion of its end edge leaves the lower die land.

ate diiilculty in succeeding drawing operations,

is to cut off the end of the drawn tube' below the thickened and bentend.

the height of each die land being insufilcient to create excessivefrictional drag, and the height of the groove between the die landsbeing such that the short side of the tube will be in contact with andsupported by a lower die land while the long side of the tube is beingformed between an upper die land and the punch. In practice, it isproposed to provide a set of die lands separated by one or more grooves,each die land having a height less than the maximum height disparitybetween the tube sides, the total axial length of said lands and grooveshaving a combined or total height at least equal to the maximumdisparity. Hence, the article is completely formed to uniform wallthickness by the upper With the above and other objects in view, an

embodiment of the invention isshown in the its cooperating punch,according to the illustrated exemplary embodiment of the invention,-

a cup to be drawn being shown in relation thereto.

Fig. 215 a-simiiar view, showing the tube partially drawn.

Fig. 3 is a similar view, showing the tube completely drawn and with itsupper end portion enthe drawing.

' Referring to the drawing, the tube drawing apparatus, of the punch anddie type illustrated by way oi example in the present disclosure,comprises a die holder. Ill provided with a down:- wardly extendingcylindrical pocket ll having a central opening H in its bottom. In thelower portion of the pocket there is engaged a die block it,superimposed by a top die and bushing member I having an annularshouldered recess I 5 at its upper side engaged by a retaining rin l6secured upon the upper side of the holder l0.

The top die and bushing member I4 is of conventional form and isprovided with a passage therethrough including an upper cylindricalentrance portion H, a downwardly converging tapered portion l8 and alower cylindrical land portion M. This member is for the purpose ofpositioning and guiding the cup 20 to the die block l3 whichincorporates the improved structure of the invention. the cup beingengaged within the passage of the upper die member and presseddownwardly therethrough through the downstroke of the punch 2?. Asillustrated, this upper die member in addition to positioning andcentering the cup is adapted to ,impart a slight preliminary draw to it.

The die block it is provided with-a vertical passage in axial alignmentwith the passage of the upper die member i6, and comprising a downwardlyconverging tapered portion 22 extending to the upper cylindrical dieland 23. 'In spaced relation below the die land 23 there is provided asecond die land 24 of identical diameter-therewith, an annular clearancegroove 25, semi-circular in cross section, being provided between theupper and lower die lands 23 and 25. Below the die land 25 there isprovided a short downwardly divergent outlet portion 25.

It is pointed out that the upper die land, which is adapted to cooperatewith the punch to draw and form the tube, is relatively narrow in orderto eliminate excessive frictional drag and excessive total compressiveforce, and in practice its axial width dimension is less than themaximum or'average disparity in height between the high and low sides ofan unevenly drawn tube. While the height of the lower die land 24 ispreferably the same as that of the upper die land it may in greater thanthe maximum or average disparity between the high and low sides of anunevenly drawn tube, so that as the tube is drawn no part of its upperend portion will leave the lower die land before the entire tube isdrawn and formed between the upper die land and the punch.

The operation is as follows:

As shown in Fig. 1 the cup 20 is slightly uneven at its upper edge, thisbeing an average condition. As this cup is drawn by the cooperatingpunch and die this unevenness increases, so that the drawn tube is ofsubstantially greater height at one side than at the other. As seen inFig. 2, the tube is partially drawn, the lower side of its upperedgejust starting to be formed between the upper die land 23 and thepunch. As seen in Fig. 3, the high side of the tube has been drawn intothe position 01 minimum clearance between the upper die land and thepunch and at the same time the low side of the tube has left the upperdie land and is being supported by the lower die land 24. As seen inFig. 4, the drawn tube is disengaged at its low side from'the lower dieland 24, and from this position the punch carries it below the die whereit is stripped from the punch as the latter is moved upwardly. It willbe seen that at all times during the'forming of the tube the punch issupported in concentric relation within the die through the support ofthe drawn tube interposed between the punch and the lower die land 24,so that there is no possibility of the punch being forced out ofconcentricity. Consequently, the tubular wall of the drawn article is ofstraight form and uniform thickness therethrough, and the drawingoperation is carried out without creating an undue stress in the die orin the drawn article. The proper positioning of the punch with the dieeliminates any possibility oi inward bending of the end portion of theshort side of the tube or of the thickening of the end portion'of itslong side. The drawn tube, may therefore be subjected to further drawingoperations without the necessity for cutting off the end, andstraightness and uniformity'oi thickness will be maintained through thesuccessive drawing operations.

In Fig. 5 is shown an alternative type of die holder such as disclosedin detail in copending application Serial No. 535,011, filed May ii,3.9%. The die holder 35 has a tapered aperture 35 which engages thetapered exterior surface iii of the die 38. The die 33 has lands and itand clearance groove M similar to that just de scribed for die block itof Figs. 1 to a, inclusive. As set forth in said copending application,the die is preferably hard and the holder relatively elastic, such as aspring steel. The taper and elasticity of the holder, hardness of thedie, downwardly converging mouth portion, area of lands, etc., arechosen so that increase of drawing pressure and impact as the work piecefirst hits the die will not affect the size of the piece being drawn,the die being movable downwardly in the holder with increase of drawingpressure and thus expanding the holder, and returnable to its freeposition upon completion of the drawing, thereby removing the stress onthe die due to the holder. By the use of the tapered die and holder, thelands are kept at a constant diameter regardless of drawing pressure soas to produce work of'a constant diameter. v

The form of the invention illustrated in the drawing and describedherein is typical and illustrative only, and it is evident that theinvention is capable of embodiments in other forms, all falling withinthe scope of the appended claims, which are to be broadly construed.

What is claimed is:

1. The method of drawing tubular article's wherein the tube wall isdrawn to a greater height at one side than the other, comprising passingthe tube through a drawing die having a drawing passage including aplurality of axially spaced annular die lands, the total height of saidlands,

and spacing being at least equal to a predetermined disparity in heightbetween the sides of annular die lands, the first of said die landsbeing of less axial height than ,a predetermined disparity in heightbetween the sides of said drawn article, and said plurality of die landsand spacing having a total axial height at least equal to saidpredetermined disparity.

3; The method of drawing tubular articles wherein the tube wall ,isdrawn to a greater height at one side than the other, comprising passingthe tube through a drawing die having 'a converging drawing passageterminating in a plurality of axially spaced annular die lands, thefirst of said die lands being of less axial height than a predetermineddisparity in height between the sides of said drawn article, saidplurality of die lands and spacing having a total axial height at leastequal to said predetermined disparity.

4. The method of drawing cup-shaped tubular articles wherein the tubewall is drawn to a greater height at one side than the other, comprisingpassing the article through a drawing die having a drawing passageincluding annular die lands having a height at least equal to a predeofdie lands and spaces therebetween having a total axial height at leastequal to said predetermined disparity.

6. The method of drawing cup-shaped tubular ammunition componentswherein the tube wall is drawn to a greater height at one side than theother, comprising passing the component through a drawing die having adrawing passage including a plurality of axially spaced annular dielands and spaces having a total height at least equal to a predetermineddisparity in height between the' sides of said drawn component.

'7. The method of drawing cup-shaped tubular articles wherein the tubewall is drawn to a greater height at one side than the other, comprisingpassing the article through a relatively nonelastic drawing die having atapered exterior surface, said die having a plurality of axially spacedannular dielands, said die lands and spaces hav- 'a total height atleast equal to a predetermined disparity in height between the sides ofsaid drawn article, and an elastic die holder having a tapered aperturefreely supporting the exterior tapered surface of said die, said holderbeing adapted to expand to enable said die to move relative theretoduring the processing of a workpiece to substantially prevent expansion.of said die.

8. A drawing die for drawing cup-shaped tubular articles wherein thetube wall is drawn to a greater height at one side than the other,having a drawing passage including a plurality of axially spaced dielands, said lands being of the same diameter, the total axial height ofsaid lands and spaces being at' least equal to a predetermined disparityin height between the two sides of said drawn article. a

9. A drawing die for drawing cup-shaped tubular ammunition components.wherein the tube wall is drawn to a greater-height at one side than theother, having a converging drawing passage terminating in a plurality ofaxially spaced annular die lands, said lands being of the same diameter,the first ofsaid die lands being of less axial height than apredetermined disparity in height between the sides of said drawnarticle, and said plurality of die lands and spacings having a totalaxial height at. least equal to said predetermined disparity.

v RAYMOND E. SLATER.

